Mechanics 1

Question 1

What is the difference between a vector and a scalar?

Answer 1

a vector is a quantity with both direction and magnitude, where a scalar is a quantity with only magnitude and no direction

Question 2

Give 3 examples of a vector

Answer 2

• velocity
• displacement
• force
• acceleration
• momentum

Question 3

Give 3 examples of a scalar

Answer 3

• speed
• direction
• mass
• time

Question 4

Define mass

Answer 4

the amount of matter in an object

Question 5

What does a free body diagram show

Answer 5

all the forces acting on that object

Question 6

Define a moment

Answer 6

a force multiplied by perpendicular distance from the point to the line of action of the force

Question 7

Define the centre of mass

Answer 7

the point at which the mass of an object, and hence its weight, appears to act

Question 8

What is the principle of moments

Answer 8

for a body in equilibrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments, about any point

Question 9

What are the two conditions for a body to be in equilibium?

Answer 9

• the sum of the clockwise moments is equal to the sum of the anticlockwise moments, about any point
• the resultant force in any direction is zero

Question 10

Define a couple

Answer 10

a pair of forces of equal size which act parallel to each other but in opposite directions

Question 11

What is a moment of couple defined as?

Answer 11

force multiplied by perpendicular distance between the lines of action of the forces

Question 12

Where is the centre of mass in a uniform, regular object?

Answer 12

at its centre

Question 13

A moment due to a couple is known as its…?

Answer 13

torque

Question 14

What is torque equal to?

Answer 14

one of the forces multiplied by perpendicular separation turning effect